Association between Liver Imaging Changes after Liver SBRT as Estimated by Area under the Dynamic Contrast-Enhanced MRI Curve and Changes in Global Liver Function

Abstract

<h3>Purpose/Objective(s)</h3> To quantify imaging changes from pre- to post-treatment dynamic contrast enhanced (DCE) MRI following liver SBRT for hepatocellular carcinoma (HCC) and examine the association with changes in albumin-bilirubin (ALBI) score. <h3>Materials/Methods</h3> Patients from a single institution treated with liver SBRT for HCC with available DCE-MRIs using a hepatocyte-specific contrast agent, Gb-EOB-DTPA, were identified. Whole liver volumetric contours were delineated on all dynamic MRI phases for pre- and post-treatment scans. Post-treatment scans were registered to the pre-treatment scans using rigid registration (median DICE coefficient 0.88, range: 0.75 to 0.95). A 3-compartment kinetic model was used to fit the signal intensity data over time from the DCE-MRI scans using the abdominal aorta as vascular input function surrogate. The area under the modeled signal intensity curve from zero to 20 minutes post contrast injection (AUC₂₀) was estimated for each individual liver voxel (∼12,000 voxels when downsampled to ∼4 × 4 × 6 mm³) and was used as an indicator of imaging-based liver function. ALBI scores were calculated from each patient's medical records at pre-treatment and at 6 months post SBRT. The association between change in AUC₂₀ throughout any part of the liver and change in ALBI score was assessed using linear regression and t-test. <h3>Results</h3> Thirty-six patients met inclusion criteria. All patients were treated in five fractions with the majority treated to a total dose of 50 Gy (70%). The median time from SBRT to analyzed post-treatment MRI scan was 6 months (range: 4-8 months). Median baseline ALBI score was -2.49 (range: -3.29 to -1.35) and the median change in ALBI score was 0.17. The average pre-treatment AUC₂₀ within all liver voxels was 3.38 (±1.36), compared to 3.09 (±1.39) at post-treatment. For most patients there was not a considerable change in median AUC₂₀, but for the patients with >30% reduction in AUC₂₀ the average worsening in ALBI score was 0.45 points. The change in AUC₂₀ was significantly correlated with the change in ALBI score at 6 months (p=0.012). Linear regression analysis adjusted for baseline ALBI score showed a significant worsening of ALBI score with increasing reduction in median AUC₂₀ (p=0.017). Patients with clinically significant worsening of ALBI score at 6 months (at least 0.5-point increase) had an average 33% reduction in median AUC₂₀ compared to an average 2% increase in AUC₂₀ for patients without clinically significant ALBI score change (p=0.014). <h3>Conclusion</h3> Post-treatment changes in MR-based liver imaging assessed by reduction in AUC₂₀ were significantly associated with change in ALBI score. This type of voxel-wise estimation of region-specific imaging features could potentially be used to improve future treatment personalization.